This invention relates to water stable vermiculite articles and the method of their manufacture. More particularly, the invention relates to water resistant vermiculite films, coatings, composites and membranes.
Vermiculite articles such as films, coatings, membranes and the like may be prepared from vermiculite dispersions by a variety of methods. Vermiculite dispersions, and methods of their use as films, coatings, etc., are described for example in U.S. Pat. Nos. 4,655,842 and 4,780,147. Such vermiculite articles tend to be unstable when exposed to water, and most will rapidly deteriorate and even disintegrate when in contact with water.
This characteristic of these vermiculite articles is disadvantageous, and may render the article unusable in applications where the film or coating will be exposed to moisture, e.g. automotive gaskets, roofing and flooring tiles, textiles and construction products. For these and similar applications it has been desired to provide vermiculite articles which are water resistant, i.e. which are able to withstand immersion in water or prolonged exposure to moisture without significant deterioration.
It is known that water resistance may be imparted to vermiculite films by treatment with polyvalent cations. U.S. Pat. No. 3,325,340 for example discloses that the water resistance of vermiculite films may be improved by treating the films with strong electrolyte solutions (greater than 1M) containing polyvalent cations such as magnesium and aluminum. U.S. Pat. No. 4,219,609 teaches that vermiculite articles may be stabilized by exposing the article to a concentrated vapor of ammonia or an alkylamine.
However, both of the above mentioned treatments suffer disadvantages. The former requires the use of strong solutions, which are costly and may cause waste disposal problems, while the latter employs irritating and potentially toxic vapors.
Thus it is an object of the present invention to provide an alternative method of imparting water resistance to vermiculite articles, without the above mentioned disadvantages.